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The Characteristics of Phospholipids

Phospholipids serve one of the most important functions in human bodies: they form the cell membranes, which help control the things that enter and exit each particular cell. Think of cell membranes as a cell protector and phospholipids as one of the main things they're composed of. In fact, as noted on the Western Kentucky University website, cell membranes are composed of trillions of phospholipid molecules.

  1. Composition

    • Phospholipids are similar to triglicerides, which are formed by combining glycerol with three fatty acids. However, a phosphate functional group is substituted for one of the three fatty acids, so the composition is different. The fatty acid tails of a phospholipid are non-polar, while the phosphate head is polar. This leads to a chemically confused molecule that's able to form a unique assembly known as a "bi-layer" when it's exposed to water. This bi-layer is what surrounds the cells.

    Phospholipid Bi-layer

    • The structure that surrounds each individual cell is formed from a phospholipid bi-layer. This occurs when the polar heads of the phospholipid face the aqueous environment on the outside of the cell and when, conversely, the non-polar tail hides from water molecules and forms a fatty layer on the inside of a cell. This is an important structure that defines the boundaries of the living and non-living portions of a cell.

    Bond

    • Phospholipids are held together by weak hydrogen bonds. These bonds are formed by the polar heads of the phospholipids and weak interactions between hydrophobic lipid molecules in the tails. The phospholipid bi-layer, which forms like a fence outside of the cell to protect it, is very flexible. It moves like a bubble in a continuous, flowing motion.

    Other Features

    • Phospholipids aren't something you can observe with the naked eye. They're small, so small that you'll need an electron microscope if you want to see and study them. Additionally, while cell membranes are made up of trillions of phospholipids, they're also composed of other things, including proteins and carbohydrates. As noted on the University of South Dakota website, carbohydrates are unique in that they can attach to either the proteins or the phospholipids in the membrane.

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